1. Field of the Invention
This invention relates to a carbon black-incorporated rubber composition having an enhanced processability and giving a vulcanizate having a satisfactory strength and rebound, and a process for the preparation of this composition.
2. Description of the Related Art
The processability of a carbon black-incorporated rubber composition and the hardness, tensile strength and rebound of the vulcanizate thereof are greatly influenced by the state of dispersion of carbon black.
The addition of a processing aid such as a process oil or a liquid rubber to a rubber composition has heretofore been adopted as the means for improving the processability of the carbon black-incorporated rubber composition. However, the addition of such a processing aid results in degradation of the physical properties of the rubber, such as the rebound.
As the means for improving the dispersibility of carbon black in a rubber composition, there has been proposed a polymer modifying process, for example, a process in which active terminals of a diene polymer are modified with a terminal modifier such as a tin halide compound, an isocyanate compound or a benzophenone derivative (see, for example, U.S. Pat. Nos. 4,550,142 and 4,647,625), Japanese Unexamined Patent Publication No. 61-141741 and Japanese Unexamined Patent Publication No. 61-293205).
However, when carbon black is incorporated with a modifier rubber as mentioned above, the Mooney viscosity of the compound stock becomes very high and the processability thereof becomes poor. It is eagerly desired to overcome this defect.